Our laboratory has been engaged in biologic, molecular and serologic studies of the AIDS-associated retrovirus (ARV). They are aimed at understanding the virus so that effective antiviral therapy and a vaccine can be developed. These efforts have led to the identification of over 300 isolates from peripheral mononuclear cells (PMC), brain tissue, and many different body fluids. They have revealed several distinctions among isolates that can be measured and need to be further studied. We shall continue ep[idemiologic and biologic studies of ARV by isolating virus from individuals over extended periods of time and evaluating any changes in the virus that may occur after infection of the host. This aspect will be approached as well by using a molecular clone of the AIDS virus in in vitro and in vivo studies. The possible existence of multiple isolates of ARV in the same individual will also be studied since development of AIDS may depend on either selected or multiple types of ARV. The biologic effect of the virus that will be examined include replicating abilities in different cells, viral interference, sensitivity to neutralization, and the nature of the cytopathology induced in certain infected cells. Moreover, the nature of latent ARV infection will be investigated. We shall examine whether the "repressed" virus can be activated by certain drugs, other viruses, graft versus host responses or other specific co-factors associated with AIDS. The results could explain the emergence of AIDS in some individuals after a long incubation period.